Temporal variability of diversity and biomass of tintinnids (Ciliophora) in a southwestern Atlantic temperate estuary

Seasonal variations in diversity and biomass of tintinnids (Ciliophora:Tintinnida) were investigated at two fixed stations in the innerpart of the Bahía Blanca Estuary (38°42' S, 61°50'W) during an annual cycle. The variations were analysed in relationto surface temperature, salinity, transparency, solar radiationand chlorophyll a (Chl a)concentration. Biomass was calculatedin terms of biovolume and carbon units. Diversity was estimatedas the number of species and the Shannon Index (H', ln based).Density of tintinnids ranged from 100 to 7800 individuals L^–1H' ranged from 0 to 1.81. The biomass varied from 0.3 to 127.78x 10⁶ µm³ L^–1 (0.02–39.4 µg C L^–1).Density was significantly related to temperature, solar radiationand Secchi distance (P < 0.01); diversity was significantlyrelated to temperature (P < 0.01) and solar radiation (P< 0.05). Biomass was significantly related only to temperature(P < 0.01) in one of the stations. According to principalcomponents analysis (PCA) tintinnids exhibited a segregationof three groups: winter, spring–summer and autumn forthe most internal station and winter, spring and summer–autumnfor the most external station. H' values were lower than thoseobserved in other coastal systems found at about the same latitudein the northern hemisphere.